Low-emissivity coatings are known in the art. Low-E coatings typically comprise at least one functional layer such as an infrared (IR) reflecting layer. The IR reflecting layer(s), or functional layer(s), may be of or based on silver or gold in typical instances. Low-E coatings are typically used in window applications such as in IG (insulating glass) window units, monolithic window, architectural windows, and/or in vehicle windows.
The thin IR reflecting layers (e.g., based on silver) are often used to reflect IR radiation. These silver-based layers are susceptible to damage, and generally require protective layers on both sides to protect them. The layer directly under and contacting the silver based IR reflecting layer in some instances is of zinc oxide doped with aluminum (ZnO:Al).
However, in a coating, the ZnO:Al layer can become stressed, which results in the formation of weak spots and contributes to a lack of overall durability. This lack of durability can result in corrosion of the coating. The silver based IR reflecting layer can become damaged, chemically and/or mechanically, due to the stress in the ZnO:Al layer. The stress of the coating can become particularly problematic during or due to thermal tempering, when the glass substrate with the coating thereon is heated to a high temperature (e.g., at least 580 degrees C.) and then rapidly cooled down.
There is therefore a need in the art for a coated article having a layer, to be located proximate or near (e.g., under) an IR reflecting layer and/or a silver based layer, that enables a coated article to realize improved durability and/or optical characteristics.